Improved algorithm for detecting zero-quantised discrete cosine transform coefficients in H.264/AVC (revised version)

In this study, an efficient approach for detecting zero-quantised discrete cosine transform (DCT) coefficients for video coding is developed. Compared with conventional detection methods of zero-quantised DCT coefficients used in H.264/AVC, the proposed algorithm has two major features. First, a new classification of patterns for DCT, quantisation, inverse quantisation and inverse discrete cosine transform processes is proposed. By taking a zigzag scanning order into the classification, the quantised DCT coefficients can be coded efficiently. Second, the thresholds for detecting zero-quantised DCT coefficients are determined by combining the Gaussian distribution with a theoretical analysis of the DCT and quantisation in H.264/AVC. Experimental results show that the proposed algorithm achieves an average timesaving of more than 40% compared with the algorithm in reference software JM12.2 of H.264/AVC. When compared with other algorithms in the literature, it also gives the best performance in terms of both rate-distortion and time saving.